#!/usr/bin/env bash
#
# setup.sh ─ 通用 systemd 注册脚本
#
# 需要 root；除 -h 以外所有参数均「显式传入」，脚本本身不带任何默认业务值。
#
# 用法示例:
#   sudo bash setup.sh \
#        --name  mysvc \
#        --bin   /opt/mysvc/mysvc \
#        --args  "-c /opt/mysvc/mysvc.yaml --log-level info" \
#        --user  nobody
#
# --------------------------------------------------------------

set -euo pipefail

############################ 参数解析 ############################

usage() {
cat <<'EOF'
用法: sudo bash setup.sh [选项]

必要参数:
  -n, --name    <service-name>    systemd 服务名
  -b, --bin     <exec-path>       可执行文件绝对路径

可选参数:
      --args    "<arg string>"    启动参数 (自动追加到 ExecStart)
  -e, --exec    "<full cmd>"      完全自定义 ExecStart, 一旦使用 --args 将被忽略
      --user    <username>        运行用户 (默认: nobody)
      --type    <simple|forking|oneshot|notify>   Service Type (默认: simple)
      --workdir <path>            WorkingDirectory
  -h, --help                      显示本帮助

示例:
  sudo bash setup.sh -n api-gw -b /srv/api-gw/bin/gw \\
                     --args "-conf /srv/api-gw/conf.toml"
EOF
exit 1
}

# 初始为空，强制调用者填写
SERVICE_NAME=""
BIN_PATH=""
ARGS=""
USER="nobody"
TYPE="simple"
WORKDIR=""
EXEC_OVERRIDE=""

while [[ $# -gt 0 ]]; do
  case "$1" in
    -n|--name)    SERVICE_NAME="$2"; shift 2;;
    -b|--bin)     BIN_PATH="$2";     shift 2;;
    --args)       ARGS="$2";         shift 2;;
    -e|--exec)    EXEC_OVERRIDE="$2";shift 2;;
    --user)       USER="$2";         shift 2;;
    --type)       TYPE="$2";         shift 2;;
    --workdir)    WORKDIR="$2";      shift 2;;
    -h|--help)    usage;;
    *)  echo "未知参数: $1" >&2; usage;;
  esac
done

# 必要参数校验
[[ -z $SERVICE_NAME || -z $BIN_PATH ]] && { echo "❌ 必须指定 --name 与 --bin" >&2; usage; }
[[ $EUID -ne 0 ]] && { echo "❌ 需要 root 权限运行" >&2; exit 1; }
[[ ! -x $BIN_PATH ]] && { echo "❌ 可执行文件不存在或不可执行: $BIN_PATH" >&2; exit 1; }

########################## systemd unit #########################

SERVICE_FILE="/etc/systemd/system/${SERVICE_NAME}.service"

if [[ -n $EXEC_OVERRIDE ]]; then
  EXEC_START="$EXEC_OVERRIDE"
else
  EXEC_START="$BIN_PATH"
  [[ -n $ARGS ]] && EXEC_START+=" $ARGS"
fi

cat >"$SERVICE_FILE" <<EOF
[Unit]
Description=$SERVICE_NAME service
After=network-online.target
Wants=network-online.target

[Service]
Type=$TYPE
User=$USER
$( [[ -n $WORKDIR ]] && echo "WorkingDirectory=$WORKDIR" )
ExecStart=$EXEC_START
Restart=on-failure
RestartSec=5s
LimitNOFILE=1048576

[Install]
WantedBy=multi-user.target
EOF

echo "✅ 已生成 $SERVICE_FILE"

########################## 启用 & 启动 ###########################

systemctl daemon-reload
systemctl enable --now "${SERVICE_NAME}.service"

echo
systemctl --no-pager status "${SERVICE_NAME}.service"